In a CMOS circuit, a p-channel FET preferably uses a Ge channel or SiGe channel having a high hole mobility for a high-speed operation. An NMOS preferably uses an Si channel having a high electron mobility.
On the other hand, in the CMOS circuit, the channel is preferably formed on an insulating layer to prevent a short channel effect. For this reason, the p-channel FET uses a GOI (Germanium On Insulator) substrate or an SGOI (Silicon Germanium On Insulator) substrate, and the n-channel FET uses an SOI (Silicon On Insulator) substrate.
However, it is difficult to inexpensively form the Ge channel or SiGe channel suitable for the p-channel FET and the Si channel suitable for the n-channel FET on one substrate.